How to use the ship ETA calculator
- Choose what to calculate: the arrival time, the speed needed to arrive on time, or the distance covered at a given speed.
- Enter the distance in nautical miles and the average speed in knots. Use the planned speed over the ground, after allowing for current and weather.
- Add the departure time and both time zones. The calculator works in UTC internally and shows the arrival in the destination port's local time, which agents and terminals use.
- Add any extra time for port calls, a canal transit, waiting at anchor or a weather margin.
The speed–distance–time formula
A knot is one nautical mile (1,852 m) per hour, so the arithmetic stays simple: at 12 knots a ship runs 288 nm a day, and a 3,000 nm passage takes 250 hours, or 10 days 10 hours.
Time zones on passage
Ships keep zone time and advance or retard the clocks as they cross time zones, while ports work in local time, which may include daylight saving. Doing the sum in UTC avoids the classic mistake of adding the passage time to a local departure time and reading the answer as local time at the other end. Check whether the destination is on summer time before you send the ETA.
Worked example
A ship leaves port at 06:00 local time (UTC+2) on 10 November 2026 for a 3,300 nm passage at 12.5 knots. The destination keeps UTC+1.
- Time at sea: 3,300 ÷ 12.5 = 264 hours = 11 days
- Departure in UTC: 06:00 − 2 h = 04:00 UTC on 10 November
- Arrival in UTC: 04:00 UTC on 21 November
- Arrival in local time: 04:00 + 1 h = 05:00 on Saturday 21 November
If the charterer needs the ship there by 06:00 local on 20 November instead, there are only 241 hours available, so the ship must average 3,300 ÷ 241 = 13.69 knots.
Why real passages take longer
- Weather, swell and adverse current reduce speed over the ground.
- Hull fouling slowly adds resistance between dry-dockings.
- Pilotage, traffic separation schemes and reporting points add distance and time.
- Canal transits need waiting time for the convoy as well as the transit itself.
Speed also drives fuel: see what a knot more or less costs with the fuel consumption calculator, and budget the canal with the Suez Canal toll calculator.